Abstract:We prove a regularity result for a Fredholm integral equation with weakly singular kernel, arising in connection with the neutron transport equation in an infinite cylindrical domain. The theorem states that the solution has almost two derivatives in L1, and is proved using Besov space techniques. This result is applied in the error analysis of the discrete ordinates method for the numerical solution of the neutron transport equation. We derive an error estimate in the L1-norm for the scalar flux, and as a con… Show more
“…The problem of optimal regularity for solutions of transport equations is a difficult subject. 6,23 In bounded domains, the solution is not arbitrarily regular, even with smooth coefficients and boundaries. Assuming that φ ∈ H 1 (Ω), the error estimate given here, up to an arbitrarily small factor η, is of the same order as that without coupling.…”
Section: Convergence Resultsmentioning
confidence: 99%
“…The framework and convergence analysis of the sequence of operators T N to T given in their paper will be the starting point of our coupling analysis. Let us also mention that optimal error estimates have been derived by M. Asadzadeh et al 6 in L 1 (Ω).…”
Section: Discrete Ordinates Methodsmentioning
confidence: 99%
“…More recently the analysis has been extended to the setting of L p spaces, which allow us to obtain more accurate and sometimes optimal error estimates. [4][5][6]18,24 The technical results obtained by Johnson and Pitkäranta 18 will be of important use here. In these works, the number of discrete ordinates was not allowed to depend on the spatial position.…”
We consider the coupling of angular discretizations of the two-dimensional linear transport equation. We show the well-posedness of the coupled problem and give an error estimate. The angular discretization is based on the discrete ordinates method. It involves a quadrature rule specifically designed for our coupling. The theory uses the integral formulation of transport and will be demonstrated on simplified geometries.
“…The problem of optimal regularity for solutions of transport equations is a difficult subject. 6,23 In bounded domains, the solution is not arbitrarily regular, even with smooth coefficients and boundaries. Assuming that φ ∈ H 1 (Ω), the error estimate given here, up to an arbitrarily small factor η, is of the same order as that without coupling.…”
Section: Convergence Resultsmentioning
confidence: 99%
“…The framework and convergence analysis of the sequence of operators T N to T given in their paper will be the starting point of our coupling analysis. Let us also mention that optimal error estimates have been derived by M. Asadzadeh et al 6 in L 1 (Ω).…”
Section: Discrete Ordinates Methodsmentioning
confidence: 99%
“…More recently the analysis has been extended to the setting of L p spaces, which allow us to obtain more accurate and sometimes optimal error estimates. [4][5][6]18,24 The technical results obtained by Johnson and Pitkäranta 18 will be of important use here. In these works, the number of discrete ordinates was not allowed to depend on the spatial position.…”
We consider the coupling of angular discretizations of the two-dimensional linear transport equation. We show the well-posedness of the coupled problem and give an error estimate. The angular discretization is based on the discrete ordinates method. It involves a quadrature rule specifically designed for our coupling. The theory uses the integral formulation of transport and will be demonstrated on simplified geometries.
“…Later research e.g. [4], [5], [6] produced analogous results for models of increasing complexity and in higher dimensions, but the proofs were mostly confined to the case of cross-sections that are constant in space. A separate and related sequence of papers (e.g.…”
We present an analysis of multilevel Monte Carlo techniques for the forward problem of uncertainty quantification for the radiative transport equation, when the coefficients (crosssections) are heterogenous random fields. To do this, we first give a new error analysis for the combined spatial and angular discretisation in the deterministic case, with error estimates which are explicit in the coefficients (and allow for very low regularity and jumps). This detailed error analysis is done for the 1D space -1D angle slab geometry case with classical diamond differencing. Under reasonable assumptions on the statistics of the coefficients, we then prove an error estimate for the random problem in a suitable Bochner space. Because the problem is not self-adjoint, stability can only be proved under a path-dependent mesh resolution condition. This means that, while the Bochner space error estimate is of order O(h η ) for some η, where h is a (deterministically chosen) mesh diameter, smaller mesh sizes might be needed for some realisations. We also show that the expected cost for computing a typical quantity of interest remains of the same order as for a single sample. This leads to rigorous complexity estimates for Monte Carlo and multilevel Monte Carlo: For particular linear solvers, the multilevel version gives up to two orders of magnitude improvement over Monte Carlo. We provide numerical results supporting the theory.
“…These schemes are usually referred to as discrete ordinate methods [3]. In particular for large scattering cross sections, these quadrature rules must ensure energy conservation in order to produce even qualitatively correct solutions.…”
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